In the good old days, Texans went to "Mexican restaurants" and ate "Mexican food." Then in 1972 The Cuisines of Mexico, an influential cookbook by food authority Diana Kennedy, drew the line between authentic interior Mexican food and the "mixed plates" we ate at "so-called Mexican restaurants" in the United States. Kennedy and her friends in the food community began referring to Americanized Mexican food as "Tex-Mex," a term previously used to describe anything that was half Texan and half Mexican. Texas-Mexican restaurant owners considered it an insult.

But by a strange twist of fate, the insult launched a success. For the rest of the world, "Tex-Mex" had an exciting ring. It evoked images of cantinas, cowboys and the Wild West. Dozens of Tex-Mex restaurants sprang up in Paris, and the trend spread across Europe and on to Bangkok, Buenos Aires and Abu Dhabi. Tortilla chips, margaritas and chili con carne are now well known around the world. In this series of articles, we reconsider Tex-Mex in light of its international reputation as America's most popular regional cuisine.

In the previous article in this series ("The French Connection," by Robb Walsh, November 23), we looked at how Parisians and their love for Tex-Mex helped to legitimize the cuisine back in Texas, where it was created.

By the early 1990s Tex-Mex was popular around the world, but here at home, it had become a victim of its own success. Canned and preprocessed ingredients like powdered refried beans, preformed taco shells and imitation cheese had become the norm as what we called Tex-Mex sank into the fast-food rut. Mom-and-pop Mexican restaurants that didn't compromise their cooking did everything they could to convince the public that what they were serving wasn't Tex-Mex.

The Southwestern cuisine movement of the mid-1980s gave Tex-Mex restaurants even more of an inferiority complex. The classically trained Southwestern chefs fused the concepts of French nouvelle cuisine with the ingredients of Mexico and the border states to create an elegant and refined new cooking style.

Despite its expense, the influence ofSouthwestern cuisine spread far beyond the confines of high-dollar restaurants. With its lobster tacos, duck enchiladas and spinach tamales, it changed the way Texans looked at familiar Tex-Mex dishes. It also created a widespread awareness of new ingredients.

Southwestern chefs imported then-exotic ingredients from Mexico like chipotle chiles, prickly pear fruit and achiote, and put them in their recipes. Then through their cookbooks and classes, the chefs taught home cooks what to do with these foods. Over the course of a decade, their innovations trickled down to the popular cuisine of the Southwest.

A new breed of Mexican restaurant opened in Texas in the early 1990s. The cooking included ingredients, such as chipotles and pasilla chiles, that had been popularized in Southwestern dishes, as well as recipes from interior Mexico, like achiote recados from Yucatán, seafood dishes from Veracruz or fruity moles from Oaxaca.

But establishments that served this updated Mexican food weren't about to call themselves Tex-Mex restaurants, even if they did continue to serve such distinctly Tex-Mex dishes as fajitas and nachos. El Rinconcito, an innovative Mexican restaurant that opened in Austin in 1991, summed up the spirit of the times with its advertising slogan: "It Ain't Tex-Mex!"

Meanwhile, many restaurants that were locked into the old-fashioned Tex-Mex style went out of business. Even such legendary institutions as The Original Mexican Restaurant in San Antonio, which had been open since 1900, and the Old Borunda Cafe in Marfa, which had been going since 1910, closed their doors permanently in the early 1990s.

And no wonder. By the 1990s the term Tex-Mex had come to define the antithesis of everything good in the evolving food scene. If the enchiladas were oozing orange grease and were served with beans refried in lard, we called it Tex-Mex. But if the enchiladas were stuffed with crabmeat and served in a green chile sauce with black beans on the side, then it was well, what was it exactly?

At The Blue Agave, the artichoke-and-spinach enchiladas are served in two-tone red and green enchilada sauce. We get some bacon-wrapped, jalapeño-stuffed shrimp, and I order a Tex-Mex combo, which includes one taco and one enchilada of your choice with two barbecue pork ribs. I get a fajita taco and a shrimp-and-spinach enchilada. Even though the ingredients sound exotic, the food has unmistakable characteristics. The dark fajita meat is seasoned, grilled well-done, cut against the grain and served in a soft flour tortilla. The enchiladas are submerged in so much molten cheese that it's difficult to distinguish any other flavors. And the pork ribs are cooked East Texas-style until the meat falls off the bone.

I am sure that The Blue Agave wants to believe it is serving something cutting-edge, and it is -- cutting-edge Tex-Mex. It is not alone. Habanero Blue and many other recently opened Mexican restaurants are following the same trend.

Diana Kennedy and the Mexican-food purists thought that once Americans tasted authentic interior Mexican food, they would never eat Tex-Mex again. They were wrong. Mexico has a fascinating cuisine, one of the best in the world. But just as our introduction to authentic northern Italian food in the 1980s didn't stop us from eating pizza, our introduction to interior Mexican food didn't interfere with our love for chips and salsa.

What happened instead is that we added those authentic Mexican dishes to the menu. Likewise, once the Southwestern cuisine got going, we added some of that stuff to our repertory, too. And now it's all mixed together into something really original. Something based on Mexican food, but uniquely Texan.

In 1998 chef David Garrido of Jeffrey's Restaurant in Austin and I published a cookbook titled Nuevo Tex-Mex (Chronicle Books). Our concept was to try to capture the modern Texas-Mexican cooking style in a recipe collection. What we call Nuevo Tex-Mex is less sophisticated than Southwestern cuisine; it's unfaithful to authentic interior Mexican cooking's fussy mandates; and it's based on such familiar Tex-Mex forms as nachos, tacos, enchiladas and fajitas -- all served with lots of margaritas and cold beer. The book is in its third printing, but Nuevo Tex-Mex hasn't exactly become a household term.

Jeffrey Steingarten, the food writer at Vogue and author of The Man Who AteEverything, once asked me if Tex-Mex was a true American regional cuisine or a displaced Mexican one. It's a good question, because it gets to the heart of our nomenclature problem.

I told him that Tex-Mex is an American regional cuisine for two reasons: First, because the ingredients that made it Tex-Mex, like flour, ground beef and yellow cheese, came from the American side of the border. And second, because Mexicans insist that it has nothing to do with their cuisine.

Tex-Mex has never received much recognition as an American regional cuisine because the term was coined to define bastardized Mexican food. People from outside the state still use it derisively. Native Texans most often use it to describe cheap, old-fashioned enchilada plates with lots of cheese and grease. But if the purpose of the term is to differentiate authentic Mexican food from the dishes created in Texas, then margaritas, nachos, cheese enchiladas, chili con carne, crispy tacos and fajitas are all Tex-Mex.

"I don't think of fajitas as Tex-Mex," a Houston writer argued with me recently. As Mama Ninfa explains (see "Mama's Got a Brand-new Bag," September 28), fajitas come from the Lower Rio Grande Valley. The name, the dish and the serving style are all uniquely Texan. But people want to call fajitas "authentic Mexican" because they think Tex-Mex means inferior. The more respectful term for fajitas and other indigenous Texas-Mexican cooking is probably "Tejano" cuisine, as in Tejano music.

Tex-Mex is an insult applied by outsiders, and for that reason, we have trouble being proud of it. But the tide has started to turn. Thanks to the popularity of Tex-Mex in Paris and around the world (see "The French Connection," November 23), Chuy's launched the proud-to-be-Tex-Mex movement, and now many others are jumping on the bandwagon. The other day I saw a billboard on the Southwest Freeway for Lucinda's, a new self-proclaimed Tex-Mex restaurant in the Village, whose slogan is "You'll think you've died and gone to San Antonio."

San Antonio may or may not be your idea of heaven. If you are interested in Tex-Mex restaurant history, Houston is a better earthly paradise. Thanks to the sheer size of our city, you can find restaurants here that illustrate almost every stage of Tex-Mex evolution -- including those still in development.

Tortilla chips sit in cute little brown bags under warming lights near the self-serve salsa bar at Taco Milagro. Once you've loaded your tray with chips and hot sauce, you walk up and order from an overhead menu that includes Tex-Mex standards like nachos, fajitas and margaritas; Cal-Mex imports like burritos and fish tacos; traditional Mexican dishes like shrimp campeche and caldo de pollo; and some Southwestern innovations like sweet-potato-and-Swiss-chard enchiladas in guajillo sauce.

Taco Milagro's spinach-and-cheese enchiladas in Tex-Mex sauce are a little bland, but the Milagro burritos I sample more than compensate. These aren't California-style burritos with sealed ends but Texas-style, open-ended soft tacos placed on the plate seam-side down. Mine are stuffed with grilled fajita meat, onions, fresh-sliced jalapeños, roasted poblano chile strips and pico de gallo. The meat is tender with a nice char, and the heat level is no-holds-barred, full-on hot as hell. I guess it's the fresh jalapeños that get me -- I spend five minutes sucking ice cubes out of my iced tea. I haven't had a taco this hot in years.

We've come a long way from the days of Felix Tijerina's gringo-friendly chili gravy (see "Combination Plates," August 31). Nowadays we seek ever more exciting taste sensations. And as always, Tex-Mex has evolved to keep pace with our tastes. But wait a minute, you say, Taco Milagro isn't Tex-Mex. Or is it?

"I consider Mexican food to be one of the finest cuisines in the world. We approach it with the utmost dedication and respect. At Taco Milagro, we offer you a little Mexico in Texas or a little Texas in Mexico," writes executive chef Robert Del Grande on the back of the menu.

Taco Milagro may be a glimpse into the future of our regional cuisine. The restaurant is a prototype of a concept being developed by the Schiller Del Grande Restaurant Group. By calling this eclectic blend of Southwestern, quasi-Mexican and Tex-Mex items "Mexican food," Del Grande and company are following an old Houston tradition.

When the Original Mexican Restaurant opened on Fannin Street in 1908, its slogan was "Genuine Mexican Food, Properly Prepared," despite the fact that in those days "genuine Mexican food" meant chili con carne. In 1929 Felix Tijerina's slogan was "For the Finest in Mexican Foods," although to this day, Felix's is best known for classic Tex-Mex cheese enchiladas in chili gravy. Which brings this series of articles on Tex-Mex full circle, back to where we started.

For almost a hundred years, the restaurants that have served Tex-Mex, in all its many colorful variations, have insisted that they serve authentic Mexican food. And judging by the menu at Taco Milagro, this trend is likely to continue. It may be confusing to newcomers, but it follows a certain Latin American logic, which understands that appearance and reality exist independently and for different reasons.

So remember this secret code: If the menu or the sign out front says, "Mexican food," it's really Tex-Mex -- just don't tell anyone.